Improve first use experience following installation of new Terminal application

### User experience revisions

On a new Windows 11 Pro 25H2 installation (with current feature updates), the setup experience was not ideal.

I installed the new Terminal app directly from the [Microsoft App Store](https://apps.microsoft.com/detail/9nmqc2ssjx24) library.

### Issue 1: Save button is grayed and user interface appears frozen. GitHub Copilot app is not installed error displayed after restarting the terminal app.

Upon installation and first configuration, I clicked the "Save button" but the UI became stuck on the greyed "Setting up..." button.

Followed by the error: "Failed to install GitHub Copilot. Check your network and try again." - this was invalid as Microsoft Edge and all other system apps have connectivity.

Fix: As a workaround I tried installing the GitHub.Copilot component manually using the suggested PowerShell script in PowerShell 7.6.2 as administrator.

```
winget install --id GitHub.Copilot --exact --silent `
--source winget `
--accept-source-agreements --accept-package-agreements `
--disable-interactivity
```
I also tried the following and applied permissions manually and restarted the machine.

`winget install GitHub.Copilot`

### Issue 2: PowerShell script permissions not added

When trying to Save settings in the Welcome screen then presented a new error "PowerShell execution policy is blocking scripts. Error detection turned off."

Fix: Manually setting the following PowerShell permissions in a new Windows PowerShell 5.1 window (and in PowersShell 7.6.2) cleared the error.

`Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned`

### Issue 3: GitHub Copilot Device validation required, but there is no button to launch device registration from the app.

I restarted the Terminal app again. It suggested that GitHub Copilot requires login, however the Settings > Agent screen did not have a button to launch the GitHub Copilot login website from the app.

```
Sign in required
Your agent "GitHub Copilot" requires authentication. Follow the steps below to sign in. To switch agents, go to
Intelligent Terminal Settings > Agent.

> Sign in to GitHub Copilot
```

Fix: Manually using the following script in a new PowerShell window opens the copilot github device activation validation via https://github.com/login/device...

`copilot login`

The experience was unintuitive and required me to lookup the GitHub documentation to simply install the app and sign-in to the application.

### Proposed technical implementation details

1. Upon installation of the Microsoft.IntelligentTerminal from winget or the Microsoft app store, automatically apply the minimum settings and user account level powershell "RemoteSigned" permissions required to configure the application and sign-in to GitHub Copilot.

2. Automatically retry installation of GitHub.Copilot from the new Terminal app on first configuration if it errored previously when the app was opened.

3. There should be a "Add Sign in to GitHub Copilot" setting in the Terminal app to sign-into the current selected Copilot service via graphical user interface (an in‑app device login feature).

In summary, all of this should be done automatically by the app installer.

```
Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned

winget install --id Microsoft.IntelligentTerminal -e

winget install --id GitHub.Copilot --exact --silent `
--source winget `
--accept-source-agreements --accept-package-agreements `
--disable-interactivity

copilot login
```

Note: At first "copilot login" was not recognised as a valid input in PowerShell, but after restarting the computer PowerShell recognised the GitHub.Copilot component was installed.